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COMPARATIVE TIMBER-YIELDS
BY I. T. HAIG
Associate Silviculturist, Northern Rocky Mountain Forest Experiment Station
The author has made an interesting comparison of the rates of growth of a number of
important American timber trees. The study indicates the richness of our native tree
flora in fast-growing conifers, and that these are not confined to any one region or type
of climate.
URING THE LAST decade the
U. S. Forest Service and several of
the forest schools have completeCI
rather comprehensive studies of the growth
and yield of a number of commercially
important native conifers. As the majority of these studies show the volumes obtainable in fully-stocked stands to very
similar standards of utilization, they furnish an excellent opportunity to compare
the relative rates of growth on a number
of important tree species. This is always
an interesting subject to many foresters,
as indicated by the Woodward-Forbes controversy1 of some months ago, and consequently the writer has felt it worth
while to bring some of the newer data together for purposes of comparison.
In this comparison only normal yield
tables, showing the volumes obtainable
in fully-stocked stands, have been used
throughout. In each instance the cubicfoot volumes include the entire peeled
contents of the tree; i. e., stump, stem
and tip, hut not hark or branches. The
hoard-foot values are, with two exceptions, in the International ¥8-inch rule
and show the contents of all trees· 7 or 8
inches and up scaled to a 5-inch top diameter. Both exceptions are to reasonably
comparable standards. In each case an
attempt has been made to choose values
for average site, but, as this is not always readily determined from tabular descriptions, minor injustices may have been
done individual species. Within these lim-
D
1
}0URNAL OF FoRESTRY,
itations Table 1 gives a fair comparison
of the relative rates of growth and yield
for a round dozen commercially-important
conifers.
Even a casual survey of the timberyields shown in Table 1 reveals two very
interesting features: ( 1) The richness of
our native flora in fast-growing conifers,
even in a list by no means complete, for
of the species for which data are given six
produce gross yields in excess of 20,000
hoard feet at 40 years and six over 50,000 board feet per acre at 100 years. (2)
The fact that valuable fast-growing species
are not confined to any one region or type
of climate. For example, both the South
and the Pacific Coast, with a wide diversity of climate and soils, are represented
among the leaders, and white pine (including both P. strobus and P. monticola)
more than holds its own in three widely
separated forest regions.
Total timber-yields, the factor emphasized in Table 1, is, however, a rather
unsatisfactory measure with which to compare rates of growth, for the numerical
rank of species derived in this way varies
markedly with the age chosen, and no
one age is equally fair to all species
alike. For this reason perhaps the best
single measure of the wood-producing capacity of a species is maxi~um average
annual growth, a value independent of all
elements of personal choice. Table 2
shows in descending order the relative
rank of the conifers listed on this basis.
Vol. 26, pp. 5-11 and 500-506. 1928.
575
576
JOURNAL OF FORESTRY
In this table a species growing in two distinct forest regions is given separately by
regions.
Under this rating, Redwood (Sequoia
sempervirens) is preeminently the fastest
growing native conifer, far surpassing its
nearest rival, Douglas fir (Pseudotsuga
taxifolia), a species that in itself maintains an extraordinarily high rate of
growth. These two species head the list
on the basis of both cubic-foot and boardfoot production, and it is doubtful if any
native conifer not yet accounted for will
be able .to displace them. Slash pine
(Pinus caribea) and white pine (Pinus
strobus in New England take the fourth
and fifth places in cubic volume production, while white pine in New England
and western white pine (Pinus monticola)
m the Northern Rocky Mountains capture,
respectively, similar places from the standpoint of board-foot yields. Four regions
and as many types of climate are represented among the first five species listed
and five widely diverse regions among
the same number of tail-enders. The latter
group includes, on the basis of boardfoot yields, shortleaf pine (Pinus echinata)
from the South, ponderosa pine (Pinus
ponderosa) from both the Northern Rocky
Mountain and California regions, red
spruce (Picea rubra) from New England,
and jack pine (Pinus banksiana) from the
Lake States. The inclusion of other species
not listed would, of course, undoubtedly
change the general position of some of
the species just named.
Relative wood-producing power alone,
as expressed in maximum average annual
growth, is not, however, a complete expression of the value of tree species as
timber producers, as the length of time
needed to reach merchantable size is also
an important factor. Some species, such
as the southern pines, tend to .attain merchantable size in short order, whereas
such species as the western yellow pine
and western white pine tend to reach merchantable size rather slowly. The larger
yields finally obtained in some cases by
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577
COMPARATIVE TIMBER-YIELDS
the slower-growing species probably do
not completely offset the longer time
necessary to produce timber large enoup:h
to log. Accordingly, some weight should
be given to this time factor. Table 3 shows
in descending order the relative standing
of the conifers listed based on the time
needed to produce in fully-stocked stands
an average tree 8 inches in diameter,
breast high. This standard is arbitrarily
chosen chiefly on the grounds that it seems
reasonably fair to all species and that in
stands with an average diameter of 8
inches about one-half the trees would be
above this limit and hence merchantable
under close standards of utilization.
Redwood again heads the list, proving
itself the species par excellence, with
some of the rapid-growing southern pines
and Douglas fir making up the remainder
of the five leading species. Loblolly (Pinus
taeda) and slash pine are particularly
fast in reaching merchantable size, with
longleaf (Pinus palustris) close behind
and white pine in New England a good
rival. It is true that there are certain
inconsistencies in the ratings shown in
Table 3. White fir (Abies concolor), for
example, is favored by the fact that only
trees 4 inches and up, and not all trees,
were used in computing average diameter;
while western white pine is handicapped
by the mixed nature of the stands in
which it grows where many tolerant trees
if small size lower the average diameter
of the stand without appreciably affecting
volume. But· on the whole the comparison
seems fairly reasonable.
Any ranking on rate of growth, therefore, should probably give due weight to
both wood-producing capacity and the.
time needed to reach merchantable size. 2
TABLE
RELATIVE WOOD-PRODUCING
CAPACITY OF TWELVE COMMERCIALLY-IMPORTANT
MAXIMUM AVERAGE ANNUAL GROWTH
Numerical
rating
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
2
Redwood
Douglas fir (Calif.)
Douglas fir (N. W.)
Slash pine
White pine (N. E.)
Loblolly pine
White fir
White pine (Lake States)
Western white pine (N. Rocky)
Shortleaf pine
Longleaf pine
Red spruce
Jack pine
Ponderosa pine (Calif.)
Ponderosa pine (N. Rocky)
Maximum
average
annual
growth
Cubic feet
310
180
170
143
136
131
128
121
118
110
101
80
79
66
59
CONIFERS IN
Numerical
rating
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Redwood
Douglas fir (N. W.)
Douglas fir (Calif.)
White pine (N. E.)
Western white pine (N. Rocky)
Loblolly pine
White fir
White pine (Lake States)
Longleaf pine
Slash pine
Shortleaf pine
Ponderosa pine (Calif.)
Red spruce
Ponderosa pine (N. Rocky)
Jack pine
TERMS
OF
Maximum
average
annual
growth
Board feet
1930
1190
962
828
760
750
750
739
~73
So7
558
350
310
298
214
"Had tire data been available for each species, an even more interesting ~:Jd valuable comparison
would have been on the basis of grades produced, and, consequently, the dollar value of the product.
It is quite probable that, on such a basis, the relative order of the species in the author's tables
would be materially altered. Ed.
578
JOURNAL OF FORESTRY
TABLE
3
RELATIVE RATE OF GROWTH BASED ON TIME NEEDED
FOR AVERAGE TREE TO REACH 8 INCHES,
BREAST HIGH
Numerical
rating
l. Redwood
2. Loblolly pine
3. Douglas fir (Calif.)
4. Slash pine
5. Douglas fir (N. W.)
6. Longleaf pine
7. White pine (N. E.)
8. Shortleaf pine
9. White fir
10. White pine (Lake States)
11. Ponderosa pine (N. Rocky)
12. Ponderosa pine (Calif.)
13. Jack pine
14. Western white pine (N. Rocky)
15. Red spruce
Number
years
needed
22
29
33
36
37
44
45
48
50
On this basis, redwood is undoubtedly
the fastest-growing conifer, with Douglas
fir and loblolly and slash pines close be
hind. These species, together with the
northern and western white pines and
white fir, form an exceptionally fast-growing group of conifers. It is interesting to
note, as previously stated, that this group
contains conifer types scattered from the
Pacific Coast to New England and from
the Lake States to the Gulf of Mexico.
53
55
65
70
78
87
How important are the mineral elements of the soil in regulating tree health
and growth? Professor Pierre Delbert (Paris Letter, Journal of the American Medical Assoc., Oct. ll, 1930, and Feb. 7, 1931) reports that in France, fertilizers are
employed to restore phosphorus, calcium and potassium to the soil deprived of these
substances by continued production of cultivated crops, but that this is seldom done
for magnesium. He believes that the high incidence of cancer in parts of France is
due to a deficiency of magnesium in the diet. Of 24 rural communes having the
most cancer, 23 have no magnesium; of 25 districts with a very low cancer incidence, 24 have a soil high in magnesium content. Soil scientists have presented
much evidence for and against the theory of a calcium-magnesium balance governing
plant growth. The fact that magnesium is an essential constituent of chlorophyll
should lead forest investigators to study the part played by magnesium in tree
growth and health.
S. B. DETWILER, U. S. Bureau of Plant Industry.